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Re: Sonnet Lite
Not sure what you are trying to do, but if you google "Setting up a Rectangular Patch Antenna in Sonnet", the first result takes you to Sonnet's knowledge base which has a tutorial for setting up a via-fed patch.
Hi Tom,
Could you explain your circuit? The picture looks like there is a via shorting out port 1, and there is no DC continuity between port 1 and port 2. Shouldn't there be some connections (wire bonds) connecting the feed lines to the spiral metal?
I also see that port 19M looks really close to the Tee junction, although it is really hard to see what is going on from your picture. Could you post your sonnet file (*.son)? Then we could zoom up on it, switch layers, etc. The line between ports 14 and 15 is quite a long distance from the rest...
Re: CPW impedance do not match between Sonnet and ADS lineca
Be aware that when there is loss (dielectric and/or metal), the Z0 and Keff values are complex. Sonnet will give you both the real and imaginary values. For Z0, I think both Linecalc and TXline give an "impedance" and a "loss", but I...
How did you generate the Sonnet and Momentum projects? Did you use one of their tools to automatically generate the projects, or did you do it by hand? If doing it by hand, I wouldn't be surprised if there is a difference in the stackup. Momentum and Sonnet handle the dielectrics associated with...
I think you will find that if you decrease your cell size (just in the Y direction), the capacitance will increase. I tried this with a simplified version (removed CPW feeds) and the capacitance increased from ~0.04 pF to ~0.05 pF. I used a cell size of 5 um by 0.25 um.
There is also a published technique for quantifying the error in an EM simulator for a capacitor. See this paper if interested:
Erik H. Lenzing and James C. Rautio, "A Model for Discretization Error in Electromagnetic Analysis of Capacitors," IEEE Transactions on Microwave Theory and...
I think you are right, that if you are close to a quarter wave and your Zc is relatively close to your Z0, you can use the simple equation. Flyhigh suggested 10<Zc <150 Ohm and +/- 10 degrees. I tried simulating a case on the extreme of this: Zc=10 ohms, 80 degree long line. This gives 86...
I am not sure how well I can explain this, but let me try it with an example:
Matched Line Case: Let's say you have a lossless line that is 20 degrees long. The voltage wave travels 20 degrees from port 1 to port 2. Since there is no reflection, S21 = 1.0 <-20°.
Unmatched Line Case: Now let's...
flyhigh: I was talking about equation 5.31 which does not use Zc (TRL characteristic impedance) or Z0 (normalizing impedance). It only uses the phase of S21. If the line is not matched, then the added reflections can modify S21 phase. Thus, you can't use S21 phase to calculate the effective...
I believe that equation is only valid when the Z0 of the transmission line equals the Z0 of the S-parameters. So if you have a 60 ohm line, but your S-parameters are 50 ohm S-parameters, you need to renormalize your S-parameters to 60 ohms. Of course, if you don't know the Z0 of you transmission...
momentum simulation problem
rfkevin,
Do you think it would make any difference that the via extends into the entire thickness of the top metal? I would have thought that it wouldn't make any difference because you have "metal intersecting metal" and the two become a single metal.
I looked up the reference but could not find the details of the antenna dimensions, including the thickness of the FR-4. But, I can answer your question about the partial ground plane. You will need to add an extra layer of air under the FR-4, and then draw the patial ground plane as a polygon...
Re: Microstrip Antenna
You could create multiple smaller polygons and then have the polygons touch each other, leaving a hole in the place where you want your slot.
If you can post your file, that would help.
A couple of pointers:
- Sonnet uses a metal box, so the four sidewalls are perfect metal. Thus, you need to keep the sidewalls a very large distance from your antenna.
- Keep the cell size less than 1/20 wavelength. If this is a single patch, then set...
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